JPH11248674A - Gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas sensor hardly causing the breakage of the electrode terminal of a detecting element and accordingly, trouble such as disconnection hardly occurs. SOLUTION: This gas sensor 1 includes a long detecting element 2 arranged inside a main metal fitting 3 and having a detecting portion D at the end for detecting components to be detected in gas to be measured. To the rear end of the detecting element 2, an electrode terminal 8 is protruded for electric connection to the detecting portion D. The protruded portion of the electrode terminal 8 is folded toward its end along the longitudinal direction of the outer periphery and one end of a conductive member 9 is joined to the folded portion 8a with a joint 40 and extended backward. Around the detecting element 2 inside the main metal fitting 3, a sealing material layer 32 is formed covering the joint 40 between the conductive member 9 and the electrode terminal 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an oxygen sensor, an HC sensor,
Sensor, such as NO _X sensor, it relates to a gas sensor for detecting a test substance in the measurement object gas.

[0002]

2. Description of the Related Art Conventionally, as a gas sensor as described above, a metal shell is disposed inside an outer cylinder, and a ceramic detecting element for detecting a component to be detected in a gas to be measured is provided inside the outer cylinder. Is known. In general, in a gas sensor having such a structure, as shown in FIG. 12A, an electrode terminal section 102 for extracting an output of the detection element 101 to the outside or supplying power to a circuit section in the detection element 101. Are provided so as to protrude from the rear end face of the detection element 101. A lead frame 103 is connected to these electrode terminals 102.
Are joined by a joining portion 105 such as a spot welded portion, and further, a lead wire (not shown) is joined to the lead frame 103, so that output is taken out or power is supplied. On the other hand, the space between the outer surface of the detection element 101 and the inner surface of the metal shell 104 is sealed with a sealing material layer 106 such as glass.

[0003]

However, FIG.
As shown in (a), in the gas sensor as described above, the joining portion 105 between the electrode terminal portion 102 and the lead frame 103 is generally exposed outside the sealing material layer 106. is there. Here, the electrode terminal portion 102 is generally formed of a metal wire such as a Pt wire, but since the electrode terminal portion 102 is integrally fired with the ceramic detection element 101, crystal grain growth occurs and the bending strength is reduced. Often have. Then, as described above, the electrode terminal portion 102 is
When the gas sensor has a large exposed structure, when an external force is applied at the time of assembling or using the gas sensor, the electrode terminal portion 102 is liable to break near the joint portion 105 or at the base end portion, and the like. There is a disadvantage that trouble easily occurs.

[0004] In this case, as shown in FIG.
However, in the case of an oxygen sensor or an air-fuel ratio sensor using an oxygen concentration cell element, the detection element 101
However, an air inlet for supplying the air to the oxygen reference electrode is often opened at the end face from which the electrode terminal portion 102 protrudes. In this case, if the surface is covered with the sealing material layer 106, sufficient oxygen cannot be supplied to the oxygen reference electrode, which causes a problem that the operation of the sensor is hindered.

An object of the present invention is to provide a gas sensor in which an electrode terminal portion of a detection element is hardly broken and a trouble such as disconnection is hardly generated.

[0006]

Means for Solving the Problems and Actions / Effects In order to solve the above-mentioned problems, a first configuration of a gas sensor according to the present invention is to dispose a component to be detected in a gas to be measured inside a metal shell. A detection element having a longitudinal shape in which a detection section to be detected is formed on the front end side is disposed, and an electrode terminal section for electrically connecting to the detection section is provided on the rear end side of the detection element so as to protrude therefrom. The protruding portion of the electrode terminal portion is folded back toward the tip end of the detection element along the longitudinal direction of its outer peripheral surface, and one end of the conducting member is joined to the folded portion at the rear side by a joining portion. Further, a sealing material layer is formed around the detection element inside the metal shell so as to cover the joint between the conductive member and the electrode terminal portion.

The sealing material layer may be made of an inorganic material, for example, a material mainly composed of glass.

In the gas sensor of the present invention, the electrode terminal projecting from the rear end of the detection element is folded toward the front end of the detection element, and the folded portion is joined to a conductive member (eg, a lead frame). A portion was formed, and the outside thereof was covered with a sealing material layer. For this reason,
When an external force is applied to the electrode terminal during assembly or use of the gas sensor, the sealing material layer prevents an excessive bending or tensile force from acting on the base end or the joint of the electrode terminal. Because of the shape, breakage of the electrode terminal portion hardly occurs, and furthermore, trouble such as disconnection hardly occurs.
In addition, the folded length of the electrode terminal portion can be set relatively large along the longitudinal direction of the detection element, and the length covered by the sealing material layer can be increased. Can be made more remarkable.

In a second configuration of the gas sensor according to the present invention, a detecting element having a detecting portion for detecting a component to be detected in the gas to be measured is formed inside the metallic shell, In the detection element, the detection section is configured as including an oxygen concentration cell element in which a detection-side porous electrode is formed on one side of the oxygen ion-conductive solid electrolyte layer, and an oxygen reference-side porous electrode is formed on the opposite side. On the other hand, an electrode lead portion made of a porous material is provided inside the detection element along the longitudinal direction, one end of which is connected to the oxygen reference side porous electrode, and the other end is provided with a detection portion of the detection element. It is formed so as to be exposed at the end opposite to the end, and a minute space is formed between the detection-side porous electrode and the oxygen-reference-side porous electrode in a direction in which oxygen is pumped into the oxygen-reference-side porous electrode. High pumping current is applied The pumped oxygen forms a predetermined level of reference oxygen concentration in the oxygen reference side porous electrode, and the oxygen passes through the electrode lead portion, and the exposed portion formed at the other end is used as a gas discharge port. From the rear end side of the detecting element, and an electrode terminal portion for electrically connecting to the detecting portion is provided so as to protrude therefrom. In part,
One end of the conducting member is joined by a joining portion and extends rearward. Around the detecting element inside the metal shell, the joining portion between the conducting member and the electrode terminal portion is covered, and the gas discharge port is not covered. Wherein a sealing material layer is formed.

[0010] The third configuration is that, inside the metallic shell,
A long detecting element is disposed on the tip side of a detecting section for detecting a component to be detected in a gas to be measured, and the detecting section of the detecting element detects on one side of the oxygen ion conductive solid electrolyte layer. The side porous electrode is configured to include an oxygen concentration cell element having an oxygen reference side porous electrode formed on the opposite side, and the detection element supplies a reference gas to the oxygen reference side porous electrode. A reference gas supply passage is formed in the inside thereof along the longitudinal direction thereof, and the reference gas supply passage is provided at the end opposite to the end where the detection portion of the detection element is provided. An opening is opened, and further, from the rear end side of the detecting element, an electrode terminal portion for electrically connecting to the detecting portion is provided so as to protrude, and a protruding portion of the electrode terminal portion is provided. , One end of the conductive member is A sealing material layer is formed around the detection element inside the metal shell so as to cover the joint between the conductive member and the electrode terminal portion and not to cover the reference gas inlet. It is characterized by having.

In the second and third configurations of the gas sensor according to the present invention, the gas discharge port or the reference gas inlet (for example, the air inlet) of the detecting element including the oxygen concentration cell element is not covered, and the conductive member and the electrode terminal are not covered. Since the sealing material layer is formed so as to cover the joint with the electrode part, if an external force is applied to the electrode terminal when assembling or using the gas sensor, excessive force may be applied to the base end or the joint of the electrode terminal. Since the sealing material layer prevents the application of an excessive bending force or tensile force, breakage of the electrode terminal portion is less likely to occur, and troubles such as disconnection are less likely to occur. In addition, since the gas discharge port or the reference gas inlet is not covered with the sealing material layer, the release of the pumped oxygen proceeds smoothly in the former case, and sufficient oxygen can be supplied to the oxygen reference electrode in the latter case. Therefore, in any case, the sensor can be operated without any problem.

In this case, the gas sensor has a reference gas inlet opening at the rear end face of the detection element, and the protruding portion of the electrode terminal portion is formed along the longitudinal direction of the outer peripheral surface toward the front end side of the detection element. In the folded portion, one end of the conductive member is joined by a joining portion and extends rearward, and further, the sealing material layer has a rear end face of the detecting element formed at a gas outlet or a reference gas inlet. In the state of being exposed at the same time, the bonding portion can be configured to be covered together with the folded portion of the electrode terminal portion.

By forming a folded portion in the electrode terminal portion,
With the formation side of the detection portion of the detection element as the front side and the opposite side as the rear side, it is possible to position the joint portion on the front side with respect to the rear end face of the detection element where the gas discharge port or reference gas introduction port is formed As a result, a structure that covers only the joint portion with the reference gas outlet or the gas inlet exposed is rationally realized. In addition, the folded length of the electrode terminal portion can be set relatively large along the longitudinal direction of the detection element, and the length covered by the sealing material layer can be increased. Can be made more remarkable.

On the other hand, the gas sensor has a notch formed in a rear end portion of the detection element, the cutout portion being open to a rear end surface and an outer peripheral surface of the detection element so as to be cut toward a front end side in a longitudinal direction of the detection element. Inside the notch, the conductive member is joined to the electrode terminal projecting into the notch by a joint, while the gas discharge port or the reference gas inlet is open at the rear end face of the detection element, The adhesive layer may be configured to cover the joint in the cutout together with the electrode terminal in a state where the rear end face of the detection element is exposed together with the gas outlet or the reference gas inlet.

In this configuration, the notch is formed as described above, and by projecting the electrode terminal portion into the notch, it is possible to position the joint portion forward of the rear end face of the detection element. Eventually, a structure that covers only the joint with the gas outlet or the reference gas inlet exposed is rationally realized.

The following content of the present invention can be added to the configuration of the gas sensor of the present invention. That is, the present invention provides a cylindrical metal shell, a detection section is formed at the tip end, and the detection section is disposed inside the metal shell in a form to protrude from one end of the metal shell. The other end of the metal shell is inserted in the axial direction from an opening formed on one end side in the axial direction, and a detection element for detecting a component to be detected in the gas to form an overlapping portion with the metal shell. An outer cylinder, and a connecting portion for airtightly connecting the metal shell and the outer cylinder at the overlapping portion, and a protruding portion projecting outward on the outer peripheral surface of the metal shell at the other end side. The end of the outer cylinder on the opening side covers at least a part of the surface of the protrusion.

The projecting portion of the metal shell contacts the opening edge of the hole when the gas sensor is inserted into the mounting hole or the like, for example, to prevent the gas sensor from dropping into the hole and to detect the detecting element. It functions as a stopper that determines the mounting position of the metal shell, and may be, for example, a flange that is formed in a flange shape along the circumferential direction from the outer peripheral surface of the metal shell.

According to the above invention, at least a part of the outer surface of the protruding portion of the metal shell is covered with the end of the outer cylinder on the opening side. Is prevented from directly adhering to the outer surface. This makes it difficult for a strong thermal shock to occur on the metallic shell side even when splashed or the like is applied, thereby making it less likely to affect the sealing material layer and the detection element, and extending the life thereof.

The joint between the outer cylinder and the metallic shell can be formed by welding such as laser welding or resistance welding, or can be formed by brazing. In this case, when the joint is formed by laser welding, the area of the contact / integration region between the outer cylinder and the metal shell can be reduced as compared with brazing, and when water droplets and the like adhere to the joint, It can be said that the quenching effect of the present invention can be more effectively suppressed, so that the present invention is more suitable.

When the projecting portion is the above-mentioned flange portion, the projecting side of the detecting portion in the axial direction of the metallic shell is defined as the front side, and the opposite side is defined as the rear side. At least the rear end surface of the flange portion may be covered. The rear end surface of the flange portion is a portion that is particularly susceptible to water droplets or the like when the sensor is mounted. By covering this with the outer cylinder end portion, thermal shock to the metal shell can be more effectively reduced.

In this case, the end of the outer cylinder on the opening side side
If the outer peripheral surface of the flange portion is covered together with the rear end surface of the flange portion, the area of the flange portion covered by the outer cylinder increases, and the thermal shock to the metal shell and the like can be more effectively reduced. . In this case, the above-described connecting portion can be formed in an annular shape along the outer peripheral surface of the flange portion. Since the joint portion is a region where the outer cylinder and the metal shell are in close contact with and integrated with each other, rapid cooling of the metal shell due to adhesion of water droplets is particularly likely to occur, and the influence of thermal shock on the inner sealing material layer tends to be large. Become. However, by forming this on the outer peripheral surface of the flange portion, the cooling at the joint portion propagates in the radial direction of the flange portion and then reaches the inner sealing material layer. The effect of becoming even more difficult is achieved. Further, if the rear end surface of the flange portion is not particularly formed with a coupling portion, the rear end surface and the end portion of the outer cylinder covering the rear end surface are merely in contact with each other without being integrated, or a slight gap is formed. Because it is formed form,
It is possible to more effectively prevent or suppress the occurrence of thermal shock in the portion of the metal shell.

Next, the outer cylinder can be formed with a stepped portion in the middle in the axial direction near the end on the opening side, and the tip end side can be made larger in diameter than the stepped portion. The flange portion can be inserted to a position where the flange portion hits the stepped portion. By inserting the flange portion into the enlarged diameter portion of the outer cylinder and stopping the rear end face against the step portion, positioning of the assembly of the outer cylinder with respect to the metal shell becomes easier. When the coupling portion is formed at a position corresponding to the outer peripheral surface or the rear end surface of the flange portion, the rear end surface of the flange portion can be formed flush with the corresponding end surface of the metal shell. This facilitates manufacture of the metal shell.

When the space between the inner surface of the metal shell and the outer surface of the detection element is sealed by a sealing material layer mainly composed of glass,
It is desirable to position the rear end position of the sealing material layer in the axial direction ahead of the rear end surface position of the flange portion. In this way, for example, even when water droplets or the like adhere to the rear end face of the flange portion, the rear end position of the sealing material layer is located behind the rear end surface of the flange portion, so that thermal shock due to rapid cooling can be prevented. It is difficult to transmit to the dressing layer. The rear end position of the sealing material layer is more desirably located on the front side than the front end surface of the flange portion.

Further, the gas sensor of the present invention can be configured so that the metallic shell is attached to the attaching portion in the following manner. That is, the metal shell is inserted into the cylindrical mounting portion having the male screw portion formed on the outer peripheral surface, and the protruding portion is brought into contact with the end surface of the mounting portion. Then, a nut member having a screw hole open at both ends and having a projecting portion formed to protrude inward along the rear end side opening edge of the screw hole is externally inserted into the outer cylinder from the rear end side. Further, by screwing this to the male screw portion of the mounting portion, the protruding portion is sandwiched and held between the end face of the mounting portion and the overhang portion of the nut member.

In the gas sensor of the present invention, various effects described below are achieved by adopting such a mounting structure. By forming the opening side end of the outer cylinder covering the protruding portion surface between the overhanging portion of the nut member and the protruding portion, the gap between the inner surface of the through hole of the nut member and the outer peripheral surface of the outer cylinder is formed. The surface of the protruding part (for example, the rear end face of the flange part)
Are not directly exposed, and the thermal shock to the metallic shell due to adhesion of water droplets or the like is more effectively alleviated. In a configuration in which the protrusion is a flange portion, the rear end surface and the outer peripheral surface of the protrusion are covered by the opening side end of the outer cylinder, and the coupling portion is formed at a position corresponding to the outer peripheral surface of the flange portion. Since the outer peripheral surface of the flange portion is covered with the nut member, it is extremely difficult for water droplets and the like to enter the portion, and as a result, thermal shock to the metal shell can be more effectively prevented or suppressed.

[0026]

Embodiments of the present invention will be described below with reference to the embodiments shown in the drawings. FIG. 1 shows an oxygen sensor 1 for detecting the concentration of oxygen in exhaust gas of an automobile or the like as an embodiment of the gas sensor of the present invention. The oxygen sensor 1 is commonly called a λ sensor or an O ₂ sensor, and includes an elongated plate-shaped ceramic element 2 (detection element), and its tip end is exposed to high-temperature exhaust gas flowing in an exhaust pipe.

The ceramic element 2 has a rectangular cross section, and as shown in FIG. 2A, an oxygen concentration cell element 21 formed in a horizontally long plate shape, and the oxygen concentration cell element 21 is activated by a predetermined activation. A heater 22 for heating to a temperature is stacked. The oxygen concentration cell element 21 is made of a solid electrolyte having oxygen ion conductivity. Such solid electrolytes include Y ₂ O ₃ and Ca
ZrO ₂ in which O is dissolved is a typical example, but other oxides of alkaline earth metals or rare earth metals and ZrO ₂
A solid solution with rO ₂ may be used. Further, ZfO _{2 serving as} a base may contain HfO ₂ . on the other hand,
The heater 22 is a known ceramic heater in which a resistance heating element pattern 23 made of a high melting point metal or conductive ceramic is embedded in a ceramic base.

The oxygen concentration cell element 21 has porous electrodes 25 and 26 having oxygen molecule dissociating ability on both sides near one end (a part protruding from the tip of the metal shell 3) in the longitudinal direction. Electrodes 2
5, 26 and the solid electrolyte portion sandwiched therebetween form the detection portion D.

From each of the porous electrodes 25, 26, an electrode lead portion 25 a, which extends along the longitudinal direction of the oxygen concentration cell element 21 and has an end reaching an end face of the oxygen sensor 1 on the mounting base end side.
26a are integrally formed. As shown in FIG. 2 (c), terminal ends of the electrode lead portions 25a and 26a have vias 26 crossing the oxygen concentration cell element 21 in the thickness direction.
b, 26b are connected to the electrode terminal portions 8, 8 buried in the middle portion in the thickness direction of the plate surface. The electrode terminal portion 8 is made of, for example, a Pt wire or the like, and has one end side embedded in the oxygen concentration cell element 21 and the other end side protruding from the end face of the element 21 as shown in FIG. Further, the protruding portion is folded back along the plate surface of the oxygen concentration cell element 21 to form a folded portion 8a. On the other hand, one end of the electrode terminal portion 8 is also electrically connected to the end portion of the lead portion 23 a for supplying electricity to the resistance heating element pattern 23 in the heater 22 in the same manner as the oxygen concentration cell element 21. The other end is folded along the plate surface of the heater 22 to form a folded portion 8a.

Such a ceramic element 2 is obtained as follows. That is, as shown in FIG.
Two green sheets 21 ′ and 21 ′ to be the oxygen concentration cell elements 21 are prepared. Then, one end of each of the metal wires 8 ′, 8 ′ such as Pt is positioned at a predetermined position where the pattern of the lead portion 23 a is to be formed on the end of the green sheet 21 ′. 21 ′, 21 ′ are laminated. Then, Pt is formed on the surface of the green sheets 21 ', 21' in a pattern shape corresponding to the electrodes 25, 26 and the electrode lead portions 25a, 26a.
Alternatively, the conductive paste layers 25 ′ and 26 ′ of a metal powder having a catalytic activity of the oxygen molecule dissociation reaction such as a Pt alloy are formed by screen printing. At this time, the metal wire 8 ',
At the corresponding position of 8 ', both green sheets 21', 2
A through hole (not shown) for forming vias 26b, 26b is formed in 1 '. As a result, the paste is filled in the through holes, and a via pattern is formed. By firing the thus obtained laminate, the oxygen concentration cell element 21 shown in FIG. 2A is manufactured (however, at this stage, the metal wires 8 ′, 8 ′).
The folded portion 8a is not formed in the electrode terminal portion 8 based on (1).

On the other hand, the heater 22 forms a conductive paste layer having a shape corresponding to the resistance heating element pattern 23 on the surface of the ceramic green sheet by screen printing, etc. It is manufactured by positioning a lead wire similar to that used for the oxygen concentration cell element 21 at a position, laminating another ceramic sheet thereon, and firing this.

As shown in FIG. 2D, the oxygen concentration cell element 21 and the heater 22 are joined to each other via a ceramic layer 27 such as ZrO ₂ ceramic or Al ₂ O ₃ ceramic. An electrode lead portion 26 is attached to the porous electrode (oxygen reference side porous electrode) 26 on the joining side.
a (which is also porous) is connected to one end of a porous electrode (detection-side porous electrode) 25 in the direction in which oxygen is pumped into the porous electrode 26 side. A small pumping current is applied. Here, the electrode lead portion 26a is located inside the detection element 2 so as to be sandwiched between the joined oxygen concentration cell element 21 and the heater 22, and the terminal surface thereof is on the mounting base end side of the detection element 2. Is exposed at the end face of the gas discharge port to form a gas discharge port 2s. Then, the pumped oxygen is released into the atmosphere from the gas discharge port 2s via the electrode lead portion 26a. As a result, the oxygen concentration in the porous electrode 26 is maintained at a value slightly higher than that in the atmosphere, and functions as an oxygen reference electrode. on the other hand,
The porous electrode 25 on the opposite side becomes a detection-side electrode that comes into contact with the exhaust gas.

As shown in FIG. 1, a folded portion 8 is formed in the electrode terminal portion 8 of the ceramic element 2 in, for example, a process of assembling the sensor 1, and a joining portion 40 formed by spot welding or the like at the folded portion 8a. As a result, the lead frame (conductive member) 9 made of a thin metal plate or the like is electrically connected to the distal end. Then, the ceramic element 2 is inserted into an insertion hole 31 formed in the metal shell 3, and between the inner surface of the insertion hole 31 and the outer surface of the ceramic element 2, a glass is hermetically sealed. And the like. And the ceramic element 2
The detection part D at the front end is formed of the metal shell 3 by the sealing material layer 32.
While being fixed in the metal shell 3 in a state protruding from the front end, the rear end is exposed from the sealing material layer 32. Thereby, the sealing material layer 32 is formed between the electrode terminal portion 8 and the lead frame 9.
And the gas discharge port 2s is not covered.

A metal protect cover 6 for covering the protruding portion of the ceramic element 2 is fixed to the outer periphery of the distal end of the metal shell 3 by laser welding or resistance welding (for example, spot welding). The cover 6 has a cap shape, and has an opening 6a formed at a tip end and a periphery thereof for guiding high-temperature exhaust gas flowing through the exhaust pipe into the cover 6. In this specification, the protruding side of the detection unit D in the axial direction of the metal shell 3 is referred to as a front side, and the opposite side is referred to as a rear side.

A flange portion 15 is formed on the outer peripheral surface of the rear end portion of the metal shell 3 along the circumferential direction as a projecting portion projecting outward. A stepped portion 18a is formed near the front end in the axial direction of the outer cylinder 18, and the front end side of the stepped portion 18a is an enlarged diameter portion 18b. The flange portion 15 is inserted inside the enlarged diameter portion 18b, the rear end surface of the flange portion 15 is abutted against the inner surface of the stepped portion 18a and is stopped. Part) 35, it is hermetically joined to the enlarged diameter part 18b. Here, the width of the welded portion 35 is set smaller than the outer peripheral surface width of the flange portion 15. Further, in the axial direction of the metal shell 3, the sealing material layer 3
The rear end position of 2 is located ahead of the front end position of the flange portion 15 (the front end position may be located ahead of the rear end position of the flange portion 15). In addition, the welded portion 35 as a joint may be formed by an annular caulked portion instead of laser welding. However, when it is used for an application requiring particularly high waterproofness, laser welding is more liquid-tight. It is more desirable because of its excellent properties.

As shown in FIG. 1, a nut member 5 is attached to the outside of the flange portion 15 of the metal shell 3.
A screw portion 5a is formed on the inner peripheral surface of the nut member 5, and a circumferentially extending portion 5c is formed on the rear end side opening edge so as to protrude inward, and an inner peripheral surface of the projecting portion 5c is formed. Form a through hole 5b. The nut member 5 is inserted from the rear end side of the outer cylinder 18 through the through-hole 5b, and is fastened to a male thread portion E2 (FIG. 3) of a mounting tubular portion E3 described later.

As shown in FIG. 1, a lead wire 10 made of Ni is electrically connected to the other end of the lead frame 9 connected to the electrode terminal portion 8 of the ceramic element 2 by a joint 41 formed by spot welding or the like. It is connected to the. The other ends of the lead wires 10 are covered with a resin, and these are integrally covered by a protective tube 17 in a converged state. Each of the lead wires 10 covered by the protection tube 17 extends to the outside through the distal end of the outer cylinder 18, and a connector plug (not shown) is connected to the tip thereof. The distal end of the outer cylinder 18 is reduced in diameter so as to cover the distal end of the protective tube 17, and a coupling portion 36 such as a welded portion or a caulked portion is formed on the outer periphery.

FIG. 3 shows an example of the state of attachment of the oxygen sensor 1 to the exhaust pipe E of the vehicle. The exhaust pipe E is formed with an insertion hole E1 for inserting a tip portion (detection section D) of the sensor 1 corresponding to the mounting position of the oxygen sensor 1. The exhaust pipe E corresponds to the periphery of the insertion hole E1.
, A cylindrical portion E3 having a male screw portion E2 formed on the outer peripheral surface is formed integrally with the cylindrical portion E3 in a protruding form. This cylindrical portion E
The inner diameter of 3 is set slightly larger than the outer diameter of the metal shell 3 and smaller than the outer diameter of the flange portion 15. At the time of mounting, the oxygen sensor 1 is inserted into the exhaust pipe E through the insertion hole E1, and the front end face of the flange portion 15 is connected to the cylindrical portion E3.
Contact with the top surface of Then, in this state, the screw portion 5a of the nut member 5 is tightened toward the flange portion 15 at the screw portion E2, so that the flange portion 15 is pressed between the cylindrical portion E3 and the overhang portion 5c of the nut member 5. -It is held and the oxygen sensor 1 is attached to the exhaust pipe E.

Hereinafter, the operation of the oxygen sensor 1 will be described. As shown in FIG. 3, the oxygen sensor 1 includes a nut member 5
Is fixed to the exhaust pipe E of the vehicle at the screw portion 5a, and a connector plug is connected to a controller (not shown) for use. When the detecting section D is exposed to the exhaust gas, the porous electrode 25 (FIG. 2) of the oxygen concentration cell element 21 comes into contact with the exhaust gas, and the oxygen concentration cell element 21 detects the oxygen concentration in the exhaust gas. The corresponding oxygen concentration cell electromotive force is generated. This electromotive force is taken out as a sensor output via the electrode terminal portions 8, 8 via the electrode lead portions 25a and 26a, and further via the lead wires 10, 10. This type of λ sensor (or O ₂ sensor) is widely used for air-fuel ratio detection because it exhibits a characteristic in which the concentration cell electromotive force changes abruptly in the vicinity where the exhaust gas composition reaches the stoichiometric air-fuel ratio. is there.

Here, as shown in FIG. 1, according to the configuration of the oxygen sensor 1 of the present invention, the joint 40 between the electrode terminal portion 8 and the lead frame 9 is sealed by the sealing material layer 32. Therefore, even when a tensile force is externally applied to the electrode terminal portion 8 when assembling or using the oxygen sensor 1, for example, the tensile force is not excessively applied to the joint portion 40, which may cause disconnection and the like. Can be difficult. Further, the folded length of the electrode terminal portions 8, 8 can be set relatively large along the longitudinal direction of the detection element 2, and the sealing material layer 3
Since the length covered by 2 can be increased, the effect of suppressing the action of bending force and tensile force on electrode terminal portions 8 can be made more remarkable. Further, since the air inlet 2s is not covered with the sealing material layer 32, the porous electrode 26 can function as an oxygen reference electrode without any trouble.

The mounting position of the oxygen sensor 1 in, for example, an automobile is an exhaust manifold or an exhaust pipe near the vehicle's foot, and the nut member 5 and the outer cylinder 18 exposed outside the pipe are in a high temperature state. It is easy to receive thermal shock such as splashing.

In the oxygen sensor 1, since the outer peripheral portion of the flange portion 15 of the metal shell 3 is covered by the enlarged diameter portion 18b of the outer cylinder 18, as shown in FIG.
Even when water droplets W and the like enter the inside through the through hole 5b of the nut member 5, the thermal shock is less likely to be transmitted to the metal shell 3 and the sealing material layer 32 due to the presence of the enlarged diameter portion 18b of the outer cylinder 18. In addition, it is possible to prevent the sealing material layer 32 from being damaged due to thermal shock.

Further, in the conventional oxygen sensor, for example, since the inside of the distal end of the outer cylinder 18 and the surface of the flange portion 15 are tightly integrated over a wide area by brazing or the like, thermal shock is applied from the outer cylinder 18. There was a disadvantage that it was easily transmitted to the metal shell 3. However, in the oxygen sensor 1, since the outer peripheral surface of the flange portion 15 and the enlarged diameter portion 18b are joined by the annular laser welding portion 35, the integrated region of the outer cylinder 18 and the metal shell 3 is welded. 35, only the other parts are in a contact state without being integrated, or have a slight gap. As a result, the thermal shock is less likely to be transmitted to the metal shell 3, and the influence on the sealing material layer 32 can be reduced.

Hereinafter, various modifications of the oxygen sensor will be described. In the configuration shown in FIGS. 4A and 4B, the oxygen concentration element 21 and the heater 22 are notched at both ends in the width direction including the end face at the rear end in the longitudinal direction. And 22c, 22
c is formed. Further, each electrode terminal portion 8 of the oxygen concentration element 21 and the heater 22 has a depth direction bottom 21
d, 21d and 22d, 22d project rearward without being folded back. Each of the lead frames 9 is connected to each of the electrode terminals 8 and the joint 40 in the cutouts 21c, 21c and 22c, 22c.

A spacer section 28 is interposed between the oxygen concentration element 21 and the heater 22, and the whole is integrated by firing. The spacer portions 28 are formed by notches 21 c, 21 c and 22 c, 22 of the oxygen concentration element 21 and the heater 22.
c has notches 28c, 28c corresponding to
An oxygen reference chamber 28a is formed at a position corresponding to No. 6. An air introduction passage (reference gas supply passage) 28b is formed in the spacer portion 28 at the center in the width direction so as to extend along its own longitudinal direction. One end of the passage 28b communicates with the oxygen reference chamber 28a, and the other end has a cutout portion. An air inlet 29 is formed in the rear end face of the convex portion 28e sandwiched between 28c, 28c.

As a result, as shown in FIG. 4 (b), in the ceramic element 2, the atmosphere is introduced from the atmosphere introduction port 29 through the atmosphere introduction path 28b into the oxygen reference chamber 28a, and the porous electrode 26 is Will function as In such a ceramic element 2, as shown in FIG. 5, the electrode terminal portion 8 is not folded back as described above, and the bonding portion 40 with the lead frame 9 is buried in the sealing material layer 32 in the air. The inlet 29 can be exposed from the sealing material layer 32. However, even in this configuration, the electrode terminal portion 8 may be formed by folding back as shown in FIG.

As shown in FIG. 4 (c), the air introduction passage 28b formed in the spacer portion 28 has a hole extending in the longitudinal direction at the middle in the thickness direction of the spacer portion 28 without opening the upper and lower surfaces. It can also be formed in a shape. In this case, the rear end surfaces of the oxygen concentration element 21 and the heater 22 are formed in a flat shape having no notch, and the electrode terminal portions 8 are formed therefrom.
Are projected straight without bending, while the spacer 2
The rear end portion 8 may be made to project from the rear end surfaces of the oxygen concentration element 21 and the heater 22.
In this case, the spacer portion 2 where the air inlet 29 is formed
The rear end face 8 is exposed from the sealing material layer, while the joint between the lead frame 9 and the electrode terminal portion 8 is embedded in the sealing material layer 32.

Next, as shown in FIG.
8b, the flange portion 15 is inserted into the inside of the flange portion 15b.
The outer cylinder 18 and the metal shell 3 may be hermetically joined by forming an annular welded portion (for example, a laser welded portion) 35 at an overlapping portion between the rear end surface 15a and the inner surface of the stepped portion 18a. . In this case, as shown in FIG. 7B, the enlarged diameter portion 18b of the outer cylinder 18 may be omitted.

As shown in FIG. 8, the metallic shell 3 can be formed with a cylindrical projecting portion 3f projecting rearward in the axial direction from the rear end face 15a of the flange portion 15. In this case, the laser welded portion 35 may be formed at a position corresponding to the outer peripheral surface of the protrusion 3f.

As shown in FIG. 9, a buffer layer made of a porous inorganic material is provided on one side (or both sides) of the sealing element layer 32 made of glass or the like in the axial direction of the ceramic element 2. 38 can also be provided. The buffer layer 38 is formed as a green compact or a porous calcined body of an inorganic substance powder such as talc (talc). As a result, even if a mechanical or thermal impact force acts on the ceramic element 2, excessive stress occurs near the boundary between the part of the ceramic element 2 covered with the sealing material layer 32 and the part that is not. Is less likely to concentrate, and the life of the ceramic element 2 can be extended. In this case, the buffer layer 38
Supporting a portion of the ceramic element 2 that is not covered by the sealing material layer 32 and displacing the portion in a direction intersecting the axis;
It is presumed that it acts to suppress the application of strong bending stress. Further, when heated / cooled in the glass sealing step, the glass constituting the sealing material layer 32, the radial direction of the ceramic element 2 or the metal shell 3, which tends to be applied to the ceramic element 2 due to the difference in shrinkage It is also considered to have a function of alleviating the compressive force or bending stress and the like. Thereby, the durability of the ceramic element 2 at the time of sealing the glass is also improved, and the production yield of the sensor can be increased.

Further, in the above embodiment, the λ sensor using only the oxygen concentration cell element as the detecting element (ceramic element) is configured, but it can be configured as another type of gas sensor element. . In this case, the lead wire of the ceramic element is formed by folding as described above, and the lead frame is joined at the folded portion, and a structure in which the joint is covered with a sealing material, or when using an oxygen reference electrode, A gas discharge port from the oxygen reference electrode or an air introduction port to the oxygen reference electrode is not covered, and at least one of a structure in which only a bonding portion is covered with a sealing material is realized. The following are some examples.

For example, in the oxygen sensor, in addition to a sensor having an oxygen concentration cell element as a detecting element, a titania or the like whose resistance value changes depending on the oxygen concentration is attached to the tip of a base portion made of a heat-resistant insulating material such as alumina. It may have a structure in which the detection unit is formed using a metal oxide, and the resistance change of the detection unit may be output as a detection signal of the oxygen concentration in the measurement gas.

FIG. 10 is a conceptual diagram in the case where the ceramic element is an all-area oxygen sensor element. In this case, the ceramic element 60 has a structure in which an oxygen pump element 61 and an oxygen concentration cell element 62 each composed of an oxygen ion-conductive solid electrolyte are opposed to each other with a measurement chamber 65 interposed therebetween. It is introduced into the measurement chamber 65 through a diffusion hole 67 made of a porous ceramic or the like. Note that reference numeral 69
Is a heater for heating the oxygen pump element 61 and the oxygen concentration cell element 62. The oxygen concentration cell element 62 measures the oxygen concentration in the measurement chamber 65 by the concentration cell electromotive force generated between the electrode 63 embedded in the element and the electrode 64 on the measurement chamber 65 side as an oxygen reference electrode. I do. On the other hand, a voltage is applied to the oxygen pump element 61 from an external power source (not shown) via the electrodes 66 and 68, and oxygen is pumped into or out of the measurement chamber 65 at a speed determined by the direction and magnitude of the voltage. It has become. And
The operation of the oxygen pump element 61 is controlled by an oxygen concentration cell element 62.
Is controlled by a control unit (not shown) based on the detected oxygen concentration in the measurement chamber 65 so that the oxygen concentration in the measurement chamber 65 is kept constant.
The oxygen concentration of the exhaust gas is detected based on the first pump current.

[0054] Further, FIG. 11 shows an example in which the ceramic element and the NO _X sensor element of two-chamber system. The ceramic element 70 is composed of an oxygen ion conductive solid electrolyte such as ZrO ₂ , in which first and second measurement chambers 71 and 72 are formed with a partition wall 71a interposed therebetween. A second diffusion hole 73 made of a porous ceramic or the like and connecting them to each other is formed. The first measurement chamber 71 is provided with a first diffusion hole 74.
Communicates with the surrounding atmosphere. A first oxygen pump element 75 having electrodes 76 and 77 is provided for the first measurement chamber 71, and an electrode 7 is provided for the second measurement chamber 72.
A second oxygen pump element 78 having 9 and 80 is located on the opposite side of the wall 71a, respectively. On the other hand, the oxygen concentration cell element 83 (the oxygen reference electrode 8 in the partition 71a) for detecting the oxygen concentration in the first measurement chamber 71 is provided on the partition 71a.
1 and a counter electrode 82 facing the first measurement chamber 71).
Are formed. Reference numeral 86 denotes a heater for heating the first oxygen pump element 75, the second oxygen pump element 78, and the oxygen concentration cell element 83.

In operation, first, a gas in the surrounding atmosphere is introduced into the first measurement chamber 71 through the first diffusion hole 74. Then, oxygen is pumped from the introduced gas by the first oxygen pump element 75. The oxygen concentration in the measurement chamber is detected by the oxygen concentration cell element 83, and the first oxygen pump element 75 controls the oxygen concentration in the gas in the first measurement chamber 71 by a control unit (not shown) based on the detected value. , so that a constant value of a degree that does not cause decomposition of nO _X, working for the oxygen pumping is controlled. As Thus oxygen is reduced by gas travels through the second diffusion hole 73 into the second measurement chamber 72, where and the NO _X and oxygen in the gas is completely decomposed, the second oxygen pump element 78 Pumps out oxygen. Detecting the concentration of the NO _X in the gas based on the pump current of the second oxygen pump element 78 at this time.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an oxygen sensor showing an example of a gas sensor of the present invention.

FIG. 2 is an explanatory view showing a structure of a ceramic element as the detection element.

FIG. 3 is an explanatory diagram showing an example of a state in which a gas sensor is attached to an exhaust pipe.

FIG. 4 is an explanatory view showing another structure of the ceramic element.

FIG. 5 is a partially enlarged explanatory view showing a modified example of the oxygen sensor.

FIG. 6 is an enlarged partial sectional view of FIG. 1;

FIG. 7 is an explanatory view showing a modified example of a formation position of a welded portion.

FIG. 8 is an explanatory view showing another modified example.

FIG. 9 is a longitudinal sectional view showing an example of an oxygen sensor in which a buffer layer is formed adjacent to a sealing material layer.

FIG. 10 is a schematic cross-sectional view showing an example in which a ceramic element is composed of an oxygen sensor element for all regions.

FIG. 11 is a schematic cross-sectional view showing an example similarly constituted by a NO _X sensor element.

FIG. 12 is an explanatory view showing a conventional oxygen sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Oxygen sensor (gas sensor) 2, 60, 70 Ceramic element (detection element) 2s Gas discharge port 29 Atmospheric inlet (reference gas inlet) 3 Metal shell 8 Electrode terminal part 8a Folding part 9 Lead frame (conductive member) 18 Outside Cylinder 21 Oxygen concentration cell element 25 Porous electrode (porous electrode on detection side) 26 Porous electrode (porous electrode on oxygen reference side) 26a Electrode lead 28b Atmospheric introduction path (reference gas supply path) 31 Insertion hole 32 Sealing material Layer 40 joint

Claims (5)

[Claims] 1. A detecting element having a detecting portion for detecting a component to be detected in a gas to be measured formed at a front end thereof is disposed inside a metal shell. An electrode terminal portion for electrically connecting to the detection portion is provided so as to protrude, and the protruding portion of the electrode terminal portion is folded toward the tip end of the detection element along the longitudinal direction of the outer peripheral surface thereof. One end of the conductive member is joined to the folded portion by a joining portion and extends rearward.Furthermore, inside the metal shell, around the detection element,
A gas sensor, wherein a sealing material layer is formed so as to cover the joint between the conductive member and the electrode terminal. 2. A detection element having a detection section for detecting a component to be detected in a gas to be measured formed on the front end side of the metal shell, wherein the detection section includes an oxygen ion It is configured to include an oxygen concentration cell element in which a detection-side porous electrode is formed on one side of the conductive solid electrolyte layer and an oxygen-reference-side porous electrode is formed on the other side, and along the longitudinal direction of the detection element. Inside thereof, an electrode lead portion made of a porous material has one end connected to the oxygen reference side porous electrode, and the other end side on the opposite side to the side on which the detection section of the detection element is provided. A pumping current is formed between the detection-side porous electrode and the oxygen-reference-side porous electrode in a direction in which oxygen is pumped into the oxygen-reference-side porous electrode. Is applied and the The pumped oxygen forms a predetermined level of reference oxygen concentration in the oxygen reference-side porous electrode, and the oxygen passes through the electrode lead portion and discharges an exposed portion formed at the other end thereof. It is configured to be released to the atmosphere from here as an outlet, and further, from the rear end side of the detection element, an electrode terminal portion for electrically connecting to the detection portion is provided so as to protrude therefrom. At the protruding portion of the electrode terminal portion, one end side of the conductive member is joined by a joining portion and extends rearward, and around the detection element inside the metal shell,
The joint portion between the conductive member and the electrode terminal portion covers,
A gas sensor, wherein a sealing material layer is formed so as not to cover the gas discharge port. 3. A detection element having a detection section for detecting a component to be detected in a gas to be measured formed on the front end side of the metal shell, wherein the detection section comprises an oxygen ion The conductive solid electrolyte layer includes a detection-side porous electrode on one side of the conductive solid electrolyte layer, and an oxygen concentration cell element on which an oxygen reference-side porous electrode is formed on the opposite side. A reference gas supply passage for supplying a reference gas to the reference side porous electrode is formed therein along its own longitudinal direction, and the reference gas supply passage is provided with the detection unit of the detection element. A reference gas inlet is opened at the end opposite to the end, and further, from the rear end side of the detection element, an electrode terminal portion for establishing electrical connection with the detection portion. Is provided to protrude,
At the protruding portion of the electrode terminal portion, one end side of the conductive member is joined by a joining portion and extends rearward, and inside the metal shell around the detection element,
The joint portion between the conductive member and the electrode terminal portion covers,
A gas sensor, wherein a sealing material layer is formed so as not to cover the reference gas inlet. 4. The reference gas introduction port is open at a rear end face of the detection element, and the protruding portion of the electrode terminal portion is formed along a longitudinal direction of an outer peripheral surface toward a tip end side of the detection element. One end of the conducting member is joined to the folded portion by a joining portion and extends rearward, and the sealing material layer extends the rear end face of the detection element to the gas discharge port or the reference gas introduction. With the mouth exposed,
The gas sensor according to claim 2, wherein the joint portion is covered together with the folded portion of the electrode terminal portion. 5. A notch opening at a rear end portion of the detection element, which is open to a rear end surface and an outer peripheral surface of the detection element, is formed so as to be cut toward a front end side in a longitudinal direction of the detection element. Inside the portion, the conducting member is joined by the joining portion with the electrode terminal portion projecting into the notch, while the gas outlet or the reference gas inlet is opened at the rear end face of the detection element. The sealing material layer, in a state where the rear end surface of the detection element is exposed together with the gas emission port or the reference gas introduction port,
The gas sensor according to claim 2, wherein the joint in the notch is covered together with the electrode terminal.